Cooling issue on highway

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SlantedDart

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Just got my new build back on the road. 6.4 swap into a dart. Breakdown is 3 row aluminum radiator. Custom fan shroud with pass throughs installed on all four corners. 180 stat. Holley efi turns on the fan at 190 and off at 185. Spall 16” single fan. Cruising around town 35mpr under it cools down within a matter of seconds. Sitting at a light cools down within seconds. Get on the freeway car will jump up to 195 and stay there.. fan is on at this point till 185 but it won’t go down from 193/195. I’ve read that the fan will cause a blockage at certain speeds.. so I did the pass throughs.. didn’t change it. Not sure what way to go next. Manually turn off the fan via switch on the freeway or make an air dam on the bottom to scoot up air? Fan blades are about 3/4 away from radiator core. Thoughts? Thanks
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What temp are you expecting? My LA runs at 192/197 all day in the central Florida heat.
 
I’d like it to run under 180 ish so my fans are not on for highway runs. Dont want the fan on for 30 min constantly. I can adjust the on/ off but I don’t want this thing to be at 200 on the city streets
 
That 6.4 comes with 203 degree thermostat stock. Means the factory doesn’t even want that engine colder than 203. If the 6.4 is stock, there’s no reason to run it colder than what the factory designed it for.

Honestly I’d be inclined to change the fan programming so it doesn’t come on until 200 and see what it maintains without the fan. Make it on at 200 and off at 195. Or on at 205 and off at 200. Still colder than the factory thermostat.
 
I’d like it to run under 180 ish so my fans are not on for highway runs. Dont want the fan on for 30 min constantly. I can adjust the on/ off but I don’t want this thing to be at 200 on the city streets
You could install a sail switch. When there is enough air flow the switch turns off the fans
 
I like the ideas guys thanks. The engine is 11.5:1 comp with a cam on e85 may be making more heat than stock. I just like it running under 200 imo. I may see if it likes it at 200 for a test and see if it maintains. Now if I keep it at 200 the 180 thermostat will always be open correct?
 
Do what you can to direct air THROUGH the radiator. After 40mph or so it wouldn’t even matter if you had a fan at all if all the air was going through the rad. Start with a cowl to hood seal.
 
Try a 195-205 thermostat. Engines run cooler on e85 anyway.
Don’t let your ‘stat run open constantly.
 
Just got my new build back on the road. 6.4 swap into a dart. Breakdown is 3 row aluminum radiator. Custom fan shroud with pass throughs installed on all four corners. 180 stat. Holley efi turns on the fan at 190 and off at 185. Spall 16” single fan. Cruising around town 35mpr under it cools down within a matter of seconds. Sitting at a light cools down within seconds. Get on the freeway car will jump up to 195 and stay there.. fan is on at this point till 185 but it won’t go down from 193/195. I’ve read that the fan will cause a blockage at certain speeds.. so I did the pass throughs.. didn’t change it. Not sure what way to go next. Manually turn off the fan via switch on the freeway or make an air dam on the bottom to scoot up air? Fan blades are about 3/4 away from radiator core. Thoughts? Thanks View attachment 1715952370View attachment 1715952371
195°? Is it puking coolant? Then it isn't overheating. Putting around town doesn't work the engine much depending how you drive it.
 
Explain please. I thought a 180 stat opens at 180 letting fluid through

Yes, if you have a 180* thermostat it starts to open at 180* as long as it’s accurate. It fully opens as it gets hotter, like all thermostats.

Once it’s open, the coolant is cooled by the radiator, fans, and airflow. All the thermostat does is keep the coolant from circulating through the radiator until the engine is up to temperature, so the engine warms up to operating temperature faster.

Once it’s open, the rest of the cooling system determines the temperature. All the thermostat does is set the low end temp.
 
195°? Is it puking coolant? Then it isn't overheating. Putting around town doesn't work the engine much depending how you drive it.
No puking coolant but I’d rather not have the fans on for a half hour on the freeway if I’m going for a good drive
 
The thermostat really has only two jobs. It remains closed for quick warmup and it helps regulate coolant temp.

I assume since this is a Gen 3 hemi swap that it is computer controlled. As such, you don't need to monkey with trying to run it cooler than the factory intended. That will booger with the whole ball of wax and it'll never run right. That computer is programmed to run that engine best in a range of temperature within itself. That's why they run higher opening temp thermostats. Running them cooler will result in driveability issues at the very least.
 
All I’m trying to do is eliminate the fans coming on on the freeway. I’ll try to raise the ON to 200 and off at 190 or something. On the freeway when the fans are on there is zero airflow through the electric fan. Sounds dumb but after doing research it all adds up.
 
The thermostat really has only two jobs. It remains closed for quick warmup and it helps regulate coolant temp.

I assume since this is a Gen 3 hemi swap that it is computer controlled. As such, you don't need to monkey with trying to run it cooler than the factory intended. That will booger with the whole ball of wax and it'll never run right. That computer is programmed to run that engine best in a range of temperature within itself. That's why they run higher opening temp thermostats. Running them cooler will result in driveability issues at the very least.
I agree. It runs with Holley efi with custom everything. No factory stuff but I get what your saying. Just trying to keep it a little cooler than normal
 
I agree. It runs with Holley efi with custom everything. No factory stuff but I get what your saying. Just trying to keep it a little cooler than normal
Have you read where Holley wants it to run? I'm sure it tells you in "there" somewhere.
 
FWIW, I 100% agree with your thought process. I want all my stuff running about as cool as I can get it. Running at 200 or 210 or whatever above that leaves you almost zero room for error. Idling in bumper to bumper traffic on a hot humid day. There's just no cushion. At least with a carburetor and distributor, you can tune it to run at cooler temps. Maybe Holley makes it tuneable to run at a lower temp. I doubt it. That's normally how EFI runs. Hot.
 
All I’m trying to do is eliminate the fans coming on on the freeway. I’ll try to raise the ON to 200 and off at 190 or something. On the freeway when the fans are on there is zero airflow through the electric fan. Sounds dumb but after doing research it all adds up.

So there isn't "zero" airflow through the fans on the freeway. That's completely untrue.

But the fan may be limiting the airflow more than it's improving it, the turbulence of the spinning blades can reduce airflow. And if the air speed coming into the fan is too high it can lower the fans efficiency too.

If the engine wants to run at 195° on the freeway, that's absolutely fine. Like I said, the stock 6.4 doesn't even open the thermostat until 203° which means it's ALWAYS running hotter than that once it's past warm up, and on those engines that means anything past a few minutes of run time. Turn the fans on at 205° and off at 200°, I bet it still runs 195° on the freeway.

I agree. It runs with Holley efi with custom everything. No factory stuff but I get what your saying. Just trying to keep it a little cooler than normal

Why? Lots of really smart people designed that engine to run at 203° or above. Maybe if you wanted absolute max power for a short time (ie, a drag race) you'd want it cooler than that. But if you're just driving around town, on the freeway etc, it's going to be better for the engine to run it at the temperature it was designed to.
 
FWIW, I 100% agree with your thought process. I want all my stuff running about as cool as I can get it. Running at 200 or 210 or whatever above that leaves you almost zero room for error. Idling in bumper to bumper traffic on a hot humid day. There's just no cushion. At least with a carburetor and distributor, you can tune it to run at cooler temps. Maybe Holley makes it tuneable to run at a lower temp. I doubt it. That's normally how EFI runs. Hot.

Zero room for error?

C'mon. You know that pressurized coolant in a radiator doesn't boil at 212° right? There's plenty of "room for error" running at 210°.
 
Zero room for error?

C'mon. You know that pressurized coolant in a radiator doesn't boil at 212° right? There's plenty of "room for error" running at 210°.
Ok, so there was my opinion mixed in. LOL I don't like one runnin that hot. Is that better? lol
 
Why? Lots of really smart people designed that engine to run at 203° or above. Maybe if you wanted absolute max power for a short time (ie, a drag race) you'd want it cooler than that. But if you're just driving around town, on the freeway etc, it's going to be better for the engine to run it at the temperature it was designed to.

I agree with all this......I still don't like it. LOL
 
I get it, most people here are into drag racing. Pro-stockers try to run 100-120° at the start of a run. Well, NASCAR runs at 300° (not kidding). Both are detrimental for the life of the engine and highly specialized to that type of racing and class rules, and those engines all get torn down after the race.

Running a normal engine cold just damages parts.

If you've got a 16 psi cap on your radiator your boiling temperature is closer to 250°F.
 
Explain please. I thought a 180 stat opens at 180 letting fluid through
As the engine warms up the thermostat keeps coolant from going into the radiator.

At some point the engine temp is warm enough to start opening the thermostat.

If the cooling system is 4x oversized the thermostat will regulate the temp to be around the thermostat temp.

Most cars are not over cooled and so the engine temp will keep rising and the thermostat opening till it is full open. if you clime a hill the temp rises. If you go down a hill the temp lowers and the thermostat will start regulating the low temp of the engine again.

The outside air temp, the BTUs the engine produced under various conditions, the BTUs the radiator - fan - water pump can transfer to the air will set the operating temp of the engine.

Example,
100 deg outside air, the engine will most likely run a few degrees hotter than on a 70deg day. On a 32deg day the thermostat keeps the engine around the thermostat temp.

Back in the day when you drove through the Mojave desert there were ( are?) Signs telling you to turn your AC off for the next so many miles. This was to help prevent cars from overheating.

As for the fans running while you are at speed. My bet at some speed the airflow into the rad/fan is greater than the fan can do on its own and the load on the fan will be deminished, get a ammeter and do some testing. Test the current draw at a stand still and again at fwy speeds.
 
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